Device for adjusting the timing of valves and internal combustion engine having such a device

ABSTRACT

A device for adjusting the timing of valves is provided with a driven camshaft ( 1 ) comprising two groups of radial cams with at least one radial cam ( 4, 6 ) each for controlling valves. The circumferential positions of the radial cams ( 4 ) on the camshaft of the first group is adjustable in reference to the circumferential positions of the radial cams ( 6 ) on the camshaft of the second group. For this purpose, the device is provided with a wobble plate mechanism ( 14 ) having two rotary bodies ( 2, 10 ) with a common rotational axis, connected to one another in a form-fitting manner by way of a wobble-plate ( 13 ). The first rotary body is connected to the first group of radial cams ( 4 ) and the second rotary body is connected to the second group of radial cams ( 6 ). Additionally, an internal combustion engine is provided, comprising two camshafts, each with a wobble plate mechanism and two groups of radial cams for adjusting the timing of valves. This results in a very flexible adjustment of the timing of valves.

BACKGROUND

The invention relates to a device for adjusting the timing of valves in an internal combustion engine. Additionally, the invention relates to an internal combustion engine having such a device.

Such a device has been known from DE 102 22 475 A1. The timing of valves can be preset with said adjustment device; however, there is a need for improvement regarding the flexibility of preset timing.

SUMMARY

Therefore, the object of the present invention is to further develop a device of the type mentioned at the outset such that its flexibility is increased with regard to the adjustment possibilities of the timing of valves.

This objective is obtained by a device according to the invention which acts on at least one driven camshaft having at least two radial cams for controlling valves, via a wobble plate mechanism with two rotary bodies connected to one another in a form-fitting fashion. The camshaft is provided with two groups of radial cams, each having at least one radial cam, with the camshaft circumferential positions of the radial cams of the first group being relatively adjustable in reference to the camshaft circumferential positions of the radial cams of the second group. The first rotary body is connected to the first group of radial cams, and the second rotary body is connected to the second group of radial cams in a friction-locked manner.

According to the invention, it has been recognized that a wobble plate mechanism is not only capable to adjust the relative rotational position of a camshaft overall, as is occurs in DE 102 22 475 A1, but it is also capable to adjust the control of radial cams on a camshaft in reference to one another with respect to their circumferential position towards one another. This allows, for example, to exactly preset relative timing and valve overlaps and to adjust them in a controlled manner. Furthermore, for example, the control of residual gasses is possible depending on operational location, charge-cycle work and, the volumetric efficiency. This optimization positively effects the crude emissions, the specific fuel consumption, and the torque. The adjustment of phases, i.e. the relative shifting of the circumferential position of the radial cams of the two groups, can occur aggressively in a very precise manner and independent from the operational condition of the motor with a closed loop position control.

A camshaft according to the invention allows any suitable arrangement of radial cams of the two groups over the length of the camshaft. Depending on the circumferential extension of the penetrating apertures a maximal relative rotation of the circumferential positions of the radial cams of the two groups to one another can be preset. Each of the rotary bodies can also be formed as a single piece at the corresponding shaft of the camshaft, resulting in a force-fitting connection.

Another construction is provided in an embodiment in which the radial cams of one of the two groups is connected to one of the valve timing gears in a torque proof manner.

A further embodiment of the wobble plates according to the invention provides that at least one of the two rotation plates is provided with a circular line of action for the form-fitting engagement by the wobble plate, in particular, with one engaging wall of the other rotation plate being allocated in the circular line of action. This results in a compact construction of the wobble plate mechanism.

This particularly applies to the wobble plate mechanism according to a further aspect of the invention in which the wobble plate mechanism has two concentrically nested circular lines of action for a form-fitting engagement of the wobble plate.

In a further embodiment of the invention, the interval of the setting of the intake valves in reference to the exhaust valves can be adjusted, and a valve overlap of the intake valves and the exhaust valves can be preset in a controlled manner.

In a further embodiment of the invention, an asynchronous operation of the valves of the cylinder allocated to the various groups can be preset. This way, for example, a controlled charge motion can be initiated, so that, for example, a turbulence or tumbling can be created in the combustion chamber of the corresponding cylinder. The adjustment possibility can positively effect the formation of mixtures, ignition conditions, and internal combustion conditions of an appropriately controlled internal combustion engine.

An internal combustion engine with two adjustable camshafts according to the invention can be adjusted in a very flexible manner regarding the timing of its valves. At least two camshafts according to the invention for controlling valves are provided, with one camshaft comprising at least one intake valve radial cam and the other camshaft comprising at least one exhaust valve radial cam. Wobble-plate mechanisms are allocated to both camshafts and cooperate with two groups of radial cams of the respective camshaft as noted above.

This flexibility is particularly achieved for the internal combustion engines in which the two groups at least comprise one radial cam per control valve of each cylinder.

Here, for example, the intervals of the control of the two intake valves and the control of the two exhaust valves can be exactly preset for a cylinder having two intake valves and two exhaust valves.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, an exemplary embodiment of the invention is explained in greater detail using the drawing. The sole FIGURE shows an axial cross-section through a camshaft having at its end a wobble plate mechanism for the adjustment of the timing of valves.

The camshaft, referred to as 1 in its entirety, is provided with an exterior hollow shaft 2, in which an interior hollow shaft 3 is coaxially nested. A multitude of first radial cams 4 are provided on the exterior hollow shaft 2. The interior hollow shaft 3 is rotatable inside the exterior hollow shaft 2 around a common longitudinal axis 5 of the two hollow shafts 2, 3. A multitude of second radial cams 6 are mounted in a torque proof manner to the interior hollow shaft 3.

The latter penetrate the exterior hollow shaft 2 through penetrating apertures 7, provided as circumferential slotted holes in the exterior hollow shaft 2.

A sprocket 8 is preferably formed in one piece at the exterior hollow shaft 2, cooperating via a control chain, not shown here, with the camshaft 1. The exterior hollow shaft 2 widens in a cascading manner towards the left side, according to the FIGURE. The left face of the exterior hollow shaft 2, according to the FIGURE, is provided with a multitude of recessed grooves 9; two of which are shown in the exterior hollow shaft 2 of the illustrated embodiment. The recessed grooves 9 are open towards the inside, i.e. towards the longitudinal axis.

A rotation plate 10 is connected in a torque proof manner to the interior hollow shaft 3, with the exterior circumferential wall thereof being formed in a cascading manner corresponding to the interior circumferential wall of the exterior hollow shaft 2 in the area of the sprocket and the recessed grooves 9. The left facing end wall of the rotation plate 10, according to the FIGURE, is formed in the manner of a geared ring. It is engaged by a geared ring 12 at the face of a wobble plate 13 of a wobble plate mechanism 14, complementary thereto. The numbers of teeth of the geared rings 11, 12 are different from one another. The geared ring 12 of the wobble plate 13 can have fifty teeth, for example, and the geared ring 11 of the rotation plate 10 can have 51 teeth. In the area of the exterior circumference, the wobble plate 13 is provided with several pins 15, each engaging the recessed grooves 9 of the exterior hollow shaft 2. Therefore, the rotation plate 10 and the exterior hollow shaft 2 represent two rotary bodies of the wobble plate mechanism 14. The recessed grooves 9 form a ring of action of the wobble plate mechanism 14, and the geared ring 11 forms a second ring of action of the wobble plate mechanism 14 concentrically nested therein. Two of the pins 15 are shown in the FIGURE. The wobble plate 13 is rotatable around a rotational axis 16, defining an acute angle with the rotational axis 5.

The wobble plate 13 is supported via an exterior axial/radial bearing 17, rotatable around the rotational axis 16 in reference to an essentially ring-shaped intermediate body 18. The latter is supported via an internal axial/radial bearing 19, rotatable in relation to the longitudinal axis 5 of an essentially sheath-shaped retention body 20. The intermediate body 18 can be rotatably driven around the longitudinal axis 5 by way of an electric motor, not shown here. An interior wall 21 of the retention body 20 is provided with a cascaded recess 22. A retention sleeve 23 of a central fastening screw 24 is supported thereon. With its help, the retention body 20 and the rotation plate 10 are mounted in a torque proof manner to the interior hollow shaft 3.

The wobble plate mechanism 14 is provided in a cup-shaped housing 25, with its exterior housing wall 26 being nested in a circumferential recess of the exterior hollow shaft 2 in the area of the recess grooves 9.

Due to the angle of the longitudinal axis 5 in reference to the rotational axis 16, the geared ring 12 of the wobble plate 13 only engages a small angular range of the geared ring 11 of the rotation plate 10. When the intermediate body 18 is driven, this area of engagement moves in the circumferential direction of the geared ring 11. Due to the different number of teeth, this motion changes the relative rotational position of the rotation plate 10 in reference to the wobble plate 13. This results in a rotation of the relative rotational position of the exterior hollow shaft 2 in reference to the interior hollow shaft 3, because the wobble plate 13 is connected torque proof via the pins 15 and the recess grooves 9 to the exterior hollow shaft 2 and the rotation plate 10 is connected in a torque proof manner to the interior hollow shaft 3. This correspondingly adjusts the relative rotational position of the first radial cams 4 in reference to the second radial cams 6. Thus, by way of driven rotation of the intermediate body 18, the timing of valves, preset by the camshaft 1, can be adjusted. As long as no rotation of the intermediate body 18 occurs, the two hollow shafts 2, 3 are connected to one another via the wobble plate 13 in a friction-locked fashion.

For example, the first radial cams 4 can operate intake valves and the second radial cams 6 can operate exhaust valves. In this case, the wobble plate 13 can adjust the timing and the valve overlaps.

Alternatively, it is possible to control certain intake valves with the first radial cams 4 and certain additional intake valves with the second radial cams 6. In this case, for example, an asynchronous operation of the intake valves is possible for an internal combustion engine having several intake valves per cylinder. Similarly, it is possible to operate certain exhaust valves with the first radial cams 4 and to operate certain other exhaust valves with the second radial cams 6. In this manner, for example, an asynchronous operation is possible for several exhaust valves per cylinder.

The last two variants are particularly suitable to be used for separate cam shafts for the intake control and/or the exhaust control. In this case, each of the two camshafts can be provided with a wobble plate mechanism according to the type referred to as wobble plate mechanism 14. 

1. Device for adjusting the timing of valves having at least one driven camshaft (1), comprising a wobble plate mechanism (14) having two rotary bodies (2, 10) connected to one another in a form-fitting fashion, the camshaft (1) is provided with two groups of radial cams (4, 6) each having at least one radial cam, with the camshaft—circumferential positions of the radial cams (4) of the first group being relatively adjustable in reference to the camshaft—circumferential positions of the radial cams (6) of the second group, the first rotary body (2) being connected to the first group of radial cams (4), and the second rotary body (10) being connected to the second group of radial cams (6).
 2. Device according to claim 1, wherein the camshaft (1) comprises: an exterior hollow shaft (2), which carries the radial cams (4) of the first group and is connected in a torque proof manner to one of the rotary bodies (2), and an interior shaft (3), which is arranged coaxially in reference to the exterior hollow shaft (2) and rotatable in reference thereto, to which the radial cams (6) of the second group are connected, the interior shaft is connected to the other rotary body (10) in a torque proof manner, and penetrating apertures (7) being provided in the exterior hollow shaft (2) for the radial cams (6) of the second group.
 3. Device according to claim 1, wherein the radial cams (4) of one of the two groups is connected to one of the valve timing gears in a torque proof manner.
 4. Device according to claim 1, wherein at least one of the two rotary bodies (2, 10) is provided with a circular line of action (9) for the form-fitting engagement by a wobble plate (13) of the wobble plate mechanism
 5. Device according to claim 4, wherein the wobble plate mechanism (14) has two concentrically nested circular lines of action (9, 11) for a form-fitting engagement of the wobble plate (13).
 6. Device according to claim 1, wherein the camshaft (1) operates at least one intake valve via at least one intake valve radial cam (4) assigned to one of the two groups, and operates at least one exhaust valve via at least one exhaust valve radial cam (6) assigned to the other group.
 7. Device according to claim 6, wherein an additional camshaft (1) is provided that operates at least one intake valve via at least one of the intake valve radial cams (4) assigned to one of the two groups, and operates at least one additional intake valve via at least one additional intake valve radial cam (6) assigned to the other group.
 8. Device according to claim 1, wherein the at least one camshaft (1) operates at least one exhaust valve via at least one of the exhaust valve radial cams (4) assigned to one of the two groups, and operates at least one additional exhaust valve via at least one additional exhaust valve radial cams (6) assigned to the other group.
 9. An internal combustion engine having a device for controlling valves, comprising one camshaft (1) including at least one intake valve radial cam and another camshaft including at least one exhaust valve radial cam, wobble-plate mechanisms (14) having two rotary bodies (2, 10) being allocated to each of the camshafts (1), respectively, and cooperating with two groups of radial cams (4, 6) of the respective camshafts, the radial cams (4) of the first group being relatively adjustable in reference to the camshaft—circumferential positions of the radial cams (6) of the second group on each of the camshafts, the first rotary body (2) of each of the respective wobble plate mechanisms being connected to the first group of radial cams (4) of each of the camshafts, and the second rotary body (10) of each of the respective wobble plate mechanisms being connected to the second group of radial cams (6) of each of the camshafts.
 10. Internal combustion engine according to claim 9, wherein the two groups comprise at least one radial cam (4, 6) per control valve of each cylinder.
 11. The device according to claim 4, wherein the at least one of the two rotary bodies (2, 10) is a rotation plate (10) with one engaging wall (11) being allocated in the circular line of action (9). 